console.log("Symbol==========================Symbol");
// symbol: 避免属性名冲突
let sym1 = Symbol("hi");
let sym2 = Symbol("hi");
console.log(sym1 === sym2); // false

let sym11 = Symbol("");
let sym12 = Symbol("");
console.log(sym11 === sym12); // false

const sym3 = Symbol("mySym3");
const symObj = {
    [sym3] : "dj",
    sym3 : "name"
};
console.log(symObj['sym3']); //name
console.log(symObj[sym3]); //dj